Preparation of a high-viscosity polyester by secondary processing on a corresponding low-viscosity polyester tends to require a complex process. For example, Chinese Patent Pub. No. CN1317030A describes a process in which a low-viscosity polyester is produced and mixed with oxazoline to form a matrix which is then blended with a high-viscosity polyester for subsequent processing. This process is cumbersome and the used oxazoline is biologically and environmentally hazardous. In order to overcome such shortcomings of the prior art, the present invention provides a method for preparation of a polyester hot-melt adhesive which has a low melting point of 130° C.-135° C., a high viscosity of 700-750 Pa·s (at 160° C.), and a partially sensitive viscosity-temperature property.